(1) Field of the Invention
This invention relates to couplers for connecting trailers to tractors, and more particularly it is concerned with a coupler suitable for connecting a trailer to a tractor in applications wherein frequent coupling and uncoupling operations need not be performed.
(2) Description of the Prior Art
With an increase in the volume of goods transported from place to place by meeting the requirements of the law of demand and supply and an increase in speed in the means of transportation handling the ever increasing volume of goods, the use of trailers each having a kind pin secured thereto for transporting these goods by means of tractors each having a coupler mounted thereto has become popular in recent years. Advances have been made in the progress of technology for increasing the safety of this means of transportation.
However, the technology developed so far aims at ensuring that the king pin is positively connected to the coupler, and it is left to the inspection carried out by the mechanics to check the parts to see if they are in good condition.
When the tractors and trailers are frequently coupled and uncoupled, it is possible to carry out inspection of various parts and supply lubricant satisfactorily. However, when a coupler of a tractor is connected to a king pin of a trailer and they remain coupled to each other over a prolonged period of time, it is impossible to carry out inspection and repair of the parts satisfactorily. Thus, difficulties would be experienced in detecting wear caused on sliding and engaging parts, thereby causing a reduction in safety and a shortening of the service life of the coupler.
Particularly, a coupler of the type which comprises a locking member inserted in a space defined between heads of a pair of jaws pivotably moved horizontally leftwardly and rightwardly, respectively, to lock the king pin so as to thereby prevent rotation of the locked jaws has suffered the disadvantage that difficulties are experienced in supplying grease or lubricant to the parts because the main parts are all located in the central portion of the underside of the main plate.